1. Technical Field
The present application relates generally to gas sterilization packaging and more specifically to venting and filtration means for such packaging.
2. Background Information
Articles such as medical devices can be held within a container e.g. a pouch to protect the contents from microbial contamination, air, moisture, etc. The container is typically sealed to provide a barrier to microbes. The container may be a pouch with contents held between two sheets that form the pouch. Typically, disposable medical equipment and implantable devices are sterilized following packaging and before transport to healthcare providers. Common forms of sterilization include irradiation, autoclaving, and treatment with a sterilizing gas, such as ethylene oxide (ETO). In order to gas sterilize articles and maintain sterility, certain containers e.g. pouches are provided with a gas permeable membrane or wall which allows introduction and removal of a sterilizing gas such as ethylene oxide. This gas permeable wall also functions as a barrier to entry of pathogens such as bacteria, viruses and other microbes. Articles such as medical devices and tools e.g. artificial joints, stents, implantable structures and equipment, surgical knives, catheters, clamps, etc. may be stored and transported in a sterile condition until needed whereupon the contents may be accessed under controlled conditions to minimize infection and introduction of undesirable organisms. These sterilizable containers often use spunbonded polyolefin polymeric sheets such as Tyvek® as a permeable membrane wall component to permit gas sterilization and to act as a microbial barrier; see e.g. European Patent EP 0785066B.
Another typical medical device package has a sheet of breathable material sealed to the peripheral edge of a tray or flexible thermoformed blister container to form a lidding. After placing and sealing an article inside, a sterilizing gas is admitted into the interior of the package through the breathable membrane.
These existing types of packaging have several disadvantages. In particular, the commonly employed material Tyvek® spun bonded polyolefin is susceptible to weakened seals and failure due to the use of elevated temperatures and steam in gas sterilization. More careful and time consuming handling must be used to minimize seal failures which negatively impacts packaging productivity and limits the speed at which such packages can be manufactured. Opening of the package for use also raises potential problems. Use of nonwoven sheet material made of individual fibers that are thermally bonded to each other may potentially result in exposure to, or formation during an opening process, of small fibers that may be deposited on the sterilized article; this a particular concern where such nonwoven spunbonded polyolefin sheets are included as a wall component and form a peelable seam. Also, spunbonded nonwovens such as Tyvek® are expensive.
Accordingly, there is a need for a more cost and labor efficient method for the packaging and sterilization of catheters, stents and other medical devices and instruments medical devices and instruments. Also, it would be desirable to utilize gas sterilization in rigid containers where such containers are preferred or in applications where use of a flexible membrane material is undesirable. Furthermore, membrane materials such as paper or Tyvek® are not very breathable i.e. have low gas flow rates and can be either fragile as in the case of certain papers, or expensive. It would be advantageous to reduce the area size of a vent relative to known breathable membrane wall components presently employed in medical gas sterilization packages while maintaining or improving gas flow in the sterilization process without sacrificing antimicrobial barrier properties.